Use About This Mac

Choose About This Mac from the Apple menu () in the upper-left corner of your screen. About This Mac shows an overview of your Mac, including the name and version of its operating system, its model name, and its serial number:

If you see an About This Mac window like the following, double-click the version number beneath “OS X” to reveal the serial number:

Use System Information

Open the System Information (or System Profiler) app from the Utilities folder of your Applications folder, or click the System Info (or More Info) button in About This Mac. Select Hardware on the left side of the window, then find the model name and serial number on the right: